Overload relay



Aug 22, 1944. M. E. BERMAN 2,356,373

OVERLOAD RELAY Filed oct. 2, 1940 2 sheets-sheet 1 A TTORNEY Aug. 22., 1944. M. E. -,Bl-:RMAN 2,356,373

ovERLoAD RELAY Filed Ot. 2, 1940 2 Sheets-Sheet 2 N V EN TOR.

A TTORNE Y Patented Aug. 22, 1944 OVERLOAD RELAY Martin E. Berman, Franklin, Pa., assignor to Joy Manufacturing Company,

Pennsylvania a corporation of Application October 2, 1940, Serial No. 359,318

7 Claims. (Cl. 175-294) This invention relates to the protection of electrical circuits and more particularly to apparatus for protecting an electrical circuit having a main feeder circuit and two or more branch circuits connected thereto.

The principal object of this invention is to provide an overload relay for electrical circuit protection which consists of one instantaneous type of overload device and at least two thermal types of overload devices, all of which function to open a single set of contacts.

Another object is to provide an overload relay for protecting an electrical circuit comprising a main feeder circuit having two or more branch circuits in which a common and single set of contacts is provided for controlling' the passage of current through said circuits.

A further object is to provide an overload relay for protecting an electrical circuit having two or more branch circuits in which a single set of contacts is adapted to be actuated by an instantaneous tripping device, and two or more thermal ripping devices, all of which are adapted to open :iid contacts on a predetermined overload in the spective circuits.

A still further object is to provide apparatus protecting an electrical circuit having two or ire branch circuits in which a single set of con- :ts controls the energizing of said circuits and instantaneous tripping device is provided for lening said contacts on an -overload in the main circuit and two or more thermal actuated tripping devices are provided in the branch circuits adapted to open said contacts on an overload in any of said branch circuits.

A still further object is to provide an overload relay having an arrangement of individual current carrying elements which are independent of each other and in which each element has one of its terminals electrically connected to one terminal of each of the other elements.

These and other objects which are hereinafter made apparent to those skilled in this particular art will be accomplished by means of this invention, all of which is described in the following specifications and illustrated in the accompanying drawings wherein:

Fig. 1 is a front elevation of a relay made in accordance with my invention;

Fig. 2 is a section taken on line II-II of Fig. 1;

Fig. 3 is a vertical section taken on line III-III of Fig. 1; and

Fig. 4 is a diagrammatic representation of an overload relay made in accordance with my invention and provided with a series of three thermal units and one instantaneous unit.

Referring to the drawings, I indicates a panel or base upon which an overload relay, made in accordance with my invention and designated in its entirety as 2, is mounted. The overload relay 2 comprises spaced posts 3 and 4 which are mounted on the panel I and carry current from a suitable source to spaced stationary contacts 5 and 6 in a suitable control circuit. The contacts 5 and 6 are normally bridged by a movable contact 'I carried on the end of an arm 8, which has its opposite endl pivoted on a pin 9, journaled in the legs of a substantially U shaped bracket I0,

which is carried by an insulating block II bolted to posts 3 and 4. The contact 'I is normally held in engagement with contacts 5 and 6 by a spring I2 circling the pin 9 and yieldably forcing the arm k8 toward the contacts 5 and 6.

The current of the feeder circuit to be protected by the relay 2, passes through coil of an electromagnet and will be more fully explained hereafter, while the current of the branch circuit being protected, or a proportionate part thereof, passes through heaters I3, carried by posts I3a mounted on the panel I, projecting upwardly into openings I4, in the insulating block I I, in position to transmit heat to a bimetallic disc I5, spanning the top of the openings I4. The discs I5 are adapted to deflect upwardly with increase in tem-4 perature, and in order to raise the arm 8, and move the contact I out of engagement with contacts 5 and 6 insulating buttons I6 (one for each of the discs I5) are mounted on the underside of the arm 8. Each button I6 normally rests on its respective disc I5 and is independently raised by its respective bimetallic disc I5 to open the contacts of the control circuit and thus provides thermal overload protection to the two branch circuits of the main feeder circuit.

The current of the main feeder circuit passes through the coil I'I of an electromagnet I8 hav-4 ing a frame I9 which is secured to the panel I above the posts 3 and 4 of the thermal portion of the relay by bolts 2U. When the current pass-k ing through the coil II exceeds a predetemined but adjustable value, the electromagnet I8 is energized raising an'armature 2| of substantially inverted channel shape in section, which is pivoted at 22 to the frame I9.

In order to move the contact 1 from engagement with the contacts 5 and 6 in the energization of the electromagnet I8, the armature 2I has a U shaped latch 23 pivotally mounted on a pin 24 extending between the legs of the armature 2l which engages a hook rigidly secured to the top of the arm 8.

From the foregoing description of my invention it is apparent that I have provided an overload relay for protecting a main feeder circuit having a plurality of branch circuits connected thereto in which a single set of contacts is provided normally connected in a control circuit of the energizing device of the said circuits.

My improved overload relay is especially adapted for use where both instantaneous and thermal types of overload protection are essential for two or more branch circuits in which each circuit requires a different value of thermal protection but where a single instantaneous device is adequate to provide short circuit protection for all the circuits together. For example, my device is particularly applicable to a machine having two or more electric motors. To provide adequate protection for each motor a thermal type tripping device is necessary for each motor to protect it against sustained overloads which might damage the motor. In addition an instantaneous tripping device must be provided on the machine to protect the motors and wiring on the machine against overload current of short circuit value which would damage the thermal tripping devices if permitted to continue for an appreciable length of time and I have found that adequate short circuit protection for the entire machine is obtained with but one instantaneous tripping device although two or more thermal tripping elements are employed in branch circuits.

It is obvious that with my improved relay the space required for proper and adequate overload devices is materially and substantially reduced by the elimination of a number of instantaneous tripping devices which take up considerable space. Since the electromagnet I8 instantaneously breaks the control circuit when the current through the coil l1 exceeds a predetermined value, and the thermal units I3-l5 break the control circuit when the current in any of the branch lines exceeds a predetermined value, and since both the instantaneous and thermal tripping devices act on a single set of contacts ccntrolling the energization of the main feeder circuit and the branch circuits it .is apparent that all circuits may be amply protected,

While I have described and shown the overload relay as having two or more thermal units in combination with one instantaneous unit, it is to be understood that any number of thermal units may be used in combination with a single or series of instantaneous tripping units, all of which open a single set of contacts, without departing from the spirit of my invention.

While I have shown my device as being mounted on a panel it is also obvious that the device can be mounted on any suitable base as desired, and that other modifications, additions, substitutions, changes and alterations may be made in the device without departing from the scope of the appended claims.

What I claim is new and desire for Letters Patent is:

1. An overload relay comprising, a stationary contact, a pivoted contact arm adapted to engage said stationary contact to close an electrical circuit, a pair of insulating buttons secured to `said arm, a bimetallic element supporting each of said buttons adapted when heated to turn said pivoted arm and open said circuits, an element for heating each of said bimetallic elements and electromagnetic means for instantaneously moving said arm away from said stationary contact.

2. An overload relay for protecting a main feeder circuit and a plurality of branch circuits connected thereto, comprising in combination a movable contact arm adapted to engage a stationary contact and close said branch and main circuits, a hook secured to said movable contact arm, an electromagnet connected to be energized respectively by the current in said main circuit, and having an armature connected to said hook, a member secured to said movable contact arm, a series of insulating buttons secured to said member, a bimetallic element for each of said buttons and upon which said buttons rest when said movable contact arm engages the stationary contact to close the main and branch circuits, and a heating unit adjacent to and in heating relation to each of said bimetallic elements, there being one heating unit in each of said branch circuits and connected thereto to be heated in accordance with the current therein.

3. An overload relay for protecting a feeder circuit and a plurality of branch circuits connected thereto, comprising in combination a stationary contact, a pivoted contact adapted to engage said stationary contact to close all of said circuits, a series of bimetallic elements, each adapted, when heated, to turn said pivoted contact and open all of said circuits, there being one bimetallic element for each of said branch circuits, means responsive to the current in each of said branch circuits for heating the bimetallic element associated therewith and means responsive to current surges in said feeder circuit for turning said pivoted contact to open all of said circuits.

4. An overload relay for protecting a feeder circuit and a plurality of branch circuits connected thereto comprising in combination a stationary contact, a movable contact adapted to engage said stationary contact and close all of said circuits, a bimetallic element for each of said branch circuits, each of said bimetallic elements being adapted, when heated, to move said movable contact and open all of said circuits, means responsive to the current in each of said branch circuits for heating the bimetallic element associated therewith and electromagnetic means connected to said feeder circuit, said electromagnetic means being adapted, when energized to move said movable contact and open all of said circuits.

5. An overload relay for protecting a feeder circuit and a plurality of branch circuits connected thereto comprising in combination a stationary contact, a movable contact adapted to engage said stationary contact and close all of said circuits, an insulating member associated with said movable contact, a bimetallic element for each of said branch circuits, each of said bimetallic elements being adapted, when heated, to move said insulating member and turn said movable contact to open all of said circuits, means responsive to the current in each of said branch circuits for heating the bimetallic element associated therewith and electromagnetic means responsive to current surges in the feeder circuit for moving said movable contact away from said stationary contact to open all of said circuits.

6. An overload relay for protecting a feeder circuit and a plurality of branch circuits connected thereto comprising in combination a stationary contact, a movable contact adapted to engage said stationary contact and close all of said circuits, an electromagnet responsive to current surges in the feeder circuit adapted when energized to move said movable contact away from said stationary contact and open all of said circuits, an insulating member associated with said movable contact, a bimetallic element for each of said branch circuits, each of said bimetallic elements being adapted, when heated, to move said insulating member and the movable contact associated therewith away from said stationary contact to open all of said circuits and a heater responsive to the current in each of said branch circuits for heating the bimetallic element asso ciated therewith,

7. An overload relay for protecting a feeder circuit and a plurality of branch circuits connected thereto comprising in combination a stationary contact, a movable contact; adapted to engage said stationary contact and close all cf said circuits, a series of insulating buttons associated with said movable Contact, a bimetallc element contacting each of said buttons and adapted, when heated, to turn said movable contact and open all of said circuits, a heater for heating each of said bimetallic elements, there being a heater connected to each of said branch circuits and electromagnetic means responsive to current surges in said feeder circuit for moving said movable contact away from said stationary contact to open all of said circuits.

MARTIN E. BERMAN.

\ CERTLFICATE oF comaxc'xfor;. Patent No. 2,556,575. August 22, 191m.

MARTIN E. BERN-AN.

It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction as follows: Page 2, first column, ,line 68, beginning with "1. An overload relay" strike out all to\ end including "contact-." in line 2, same page, second column, comprising claim l; and for the claims now numbered 2, "5, "li", "5", "6" and "7 ing to the printed specification, line 7, for "7 Claims" read --6 Claims--g and that the said Letters Patent. should be read with this correction therein that the seme may conform to the record of the case in the Patent Office.

signed en@ sealed this 10th day of April, A. D. 19Lr5.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFICATE oF CORRECTION. t

Patent No. 2,556,575. ugust 22, 19h14..

MARTIN E. BERMAN.

It is hereby certified thatl error appears in th' printedcspecification of the above numbered patent requiring correction as follows: Page 2, first 'column, lline 68, beginning with "l, An'overload relay" strike out all to and including "contact," in line 2, same page, second column, comprising claim l; and for the claims now numbered "2", "5, "li", "5", "6 and "7" ing to the printed specification, line 7, for "Y Claims" read --6 Claims;

and that the said Letters Patent. should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

signed and sealed this 10th day of April, A. D. 1915.

Leslie Frazer (Seal) Acting Commissioner of Patents. 

